1. Field of the Invention
This invention relates to a shoe for a crawler belt or chain, hereinafter referred to as "crawler shoe" used in an endless track vehicle, such as a construction or agricultural machine or the like.
2. Description of the Related Art
As shown in FIG. 2, in the prior art, such an endless track vehicle has crawler belts or chains, each of which has a plurality of crawler shoes 10 mounted thereon. Each crawler shoe 10 comprises a metal shoe 11 made of iron or the like having a plurality of integral projections 11a, 11b that project towards the ground contact side of the shoe and an elastic shoe 12 made of a rubber or the like, integrally molded and fixed to the metal shoe 11 around the projections on its ground contact side, so as to prevent a paved road from being damaged by the crawler shoe 10. The elastic shoe 12 and the metal shoe 11 of the crawler shoe 10 have bolt inserting screw holes (not shown) that penetrate through them for mounting one on the other. The crawler shoes 10 are connected to each other, in turn, by means of links 30 and pins 20 with bolts and nuts to constitute an endless crawler belt or chain.
In such a conventionally known crawler shoe 10, elastic shoe 12 has rounded or convex portions 13 on the surface of the respective ends of the shoe in the traveling direction (i.e., at the corners or intersections between the side surfaces 14 that extend in a direction transverse to the traveling direction and the ground contact surface 15). As shown, there is a difference between the rubber thickness of the elastic shoe 12 above the projections 11a and 11b and the rubber thickness of the elastic shoe 12 in the areas between the projections. Thus, when the elastic shoe 12 comes into contact with a road surface 50, the stresses exerted on the rubber will be concentrated in the areas above the projections.
In addition, when a crawler shoe 10, extended around a driving or idler sprocket 40, comes into contact with a road surface 50 at a "final link plunge angle .theta.", the leading rounded end portion 13 of the elastic shoe 12 in the traveling direction will strike the road first and be compressed between the road surface 50 and a first projection 11a on the metal shoe 11. This subjects the rubber around this portion 13 to an expansion strain or deformation due to the shearing forces encountered.
The "final link plunge angle .theta." is the angle of a link 30 when the immediately preceding link 30a is in a position parallel to the road surface 50 and its shoe 12a is in contact with the surface and is represented as follows: .theta.=360.degree./n, where n=number of links that would fit around sprocket 40.
Therefore, during traveling on a gravel road, if pebbles or the like on the road are encountered by the leading side faces 14 of the elastic shoes 12, the rubber there will be deformed and sometimes a part of the rubber may be broken off.